2019-07-12, 15:54
Plated-through hole reliability:
After having poor results with both ferrite and large loops (station 1808), the Magnetic sensor pre-amp was removed and examined on a bench with a few millivolts input at 10kHz. It was discovered that the magnetic sensor preamps were functioning as attenuators rather than as amplifiers. Further investigation showed that the plated-through holes supplying 3.3 volts to the 4531's showed no continuity. These were then wired-through and the preamplifiers then functioned as expected. A similar (but intermittent) issue was found on one of the RJ-45 pins. This was remedied by applying flux to the top side of the affected pin and reheating the pin. The flux drew solder from the lower pad through the missing plating to the top connection. Cabling and environmental performance is currently being evaluated before returning the preamps to service.
.... Be aware there are apparently boards that may have marginal plated-through connections.
After having poor results with both ferrite and large loops (station 1808), the Magnetic sensor pre-amp was removed and examined on a bench with a few millivolts input at 10kHz. It was discovered that the magnetic sensor preamps were functioning as attenuators rather than as amplifiers. Further investigation showed that the plated-through holes supplying 3.3 volts to the 4531's showed no continuity. These were then wired-through and the preamplifiers then functioned as expected. A similar (but intermittent) issue was found on one of the RJ-45 pins. This was remedied by applying flux to the top side of the affected pin and reheating the pin. The flux drew solder from the lower pad through the missing plating to the top connection. Cabling and environmental performance is currently being evaluated before returning the preamps to service.
.... Be aware there are apparently boards that may have marginal plated-through connections.